Anal. Chem. 2008, 80, 5232–5239
Technical Notes Coupling a High-Temperature Catalytic Oxidation Total Organic Carbon Analyzer to an Isotope Ratio Mass Spectrometer To Measure Natural-Abundance δ13C-Dissolved Organic Carbon in Marine and Freshwater Samples Robert J. Panetta, Mina Ibrahim, and Yves Ge ´ linas* GEOTOP and Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke Street West, Montre´al, Que´bec, Canada, H4B 1R6 The stable isotope composition of dissolved organic carbon (δ13C-DOC) provides powerful information toward understanding carbon sources and cycling, but analytical limitations have precluded its routine measurement in natural samples. Recent interfacing of wet oxidation-based dissolved organic carbon analyzers and isotope ratio mass spectrometers has simplified the measurement of δ13CDOC in freshwaters, but the analysis of salty estuarine/ marine samples still proves difficult. Here we describe the coupling of the more widespread high-temperature catalytic oxidation-based total organic carbon analyzer to an isotope ratio mass spectrometer (HTC-IRMS) through cryogenic trapping of analyte gases exiting the HTC analyzer for routine analysis of δ13C-DOC in aquatic and marine samples. Targeted elimination of major sources of background CO2 originating from the HTC analyzer allows for the routine measurement of samples over the natural range of DOC concentrations (from 40 µM to over 2000 µM), and salinities (
